<!DOCTYPE html>
<html>
<head>
    <title>CSS Rules Example</title>
    <style type="text/css">
        div.box {
            background-color: blue;
            width: 100px;
            height: 200px;
        }
    </style>
    <script type="text/javascript">
    
        function insertRule(sheet, selectorText, cssText, position){
            if (sheet.insertRule){
                sheet.insertRule(selectorText + "{" + cssText + "}", position);
            } else if (sheet.addRule){
                sheet.addRule(selectorText, cssText, position);
            }
        }
        
        function deleteRule(sheet, index){
            if (sheet.deleteRule){
                sheet.deleteRule(index);
            } else if (sheet.removeRule){
                sheet.removeRule(index);
            }
        }
            
        function addNewRule(){        
            var sheet = document.styleSheets[0];
            insertRule(sheet, "body", "background-color: silver;", 0);       
            //Note: Opera < 9.5 doesn't add the rule in the correct location     
        }
        
        function removeFirstRule(){
            var sheet = document.styleSheets[0];
            deleteRule(sheet, 0);           
        }

    </script>
</head>
<body>
    <div class="box"></div>
    <input type="button" value="Add CSS Rule" onclick="addNewRule()">
    <input type="button" value="Remove CSS Rule" onclick="removeFirstRule()">
    
</body>
</html>
